Elderberry (Sambucus genus) is a plant that grows as a shrub although it can be pruned and trimmed into a single stemmed tree. Only two parts of the plant are edible, ripe berries and its blossoms. The ripe berries are high in antioxidants known as anthocyanins. Consume the berries when ripe only after being cooked. The wood, roots, bark, leaves and stems are toxic. Those parts contain cyanogenic glycosides that are known to be poisonous.
Wikipedia has a very good entry on Elderberry. https://en.wikipedia.org/wiki/Sambucus
Elderberry has many traditional uses in food in Europe. The berries are used in pies and other baked goods, wine, drinks and soft drinks. The flower or blossoms are used to flavor drinks and liqueurs.
Elderberry have a traditional use not only as a fruit but as a natural medicine. Being high in antioxidants, elderberries have been used to treat common illness such as colds and the flu and are thought to have anti-inflammatory properties. Here is an article on the health benefits of elderberry.
https://www.verywellhealth.com/elderberry-for-colds-and-flu-can-it-help-89559
Here is what WebMD has about Elderberry. https://www.webmd.com/vitamins/ai/ingredientmono-434/elderberry
In my backyard orchard I need to fence my trees and shrubs to prevent damage by rabbits. I do not need to fence the elderberry. The rabbits will not chew or eat the bark on the elderberries! This experience is in line with the bark and wood being toxic.
I got my elderberry seedlings (Sambucus canadensis) from Cold Stream Farms.
https://www.coldstreamfarm.net/product/black-elderberry-sambucus-canadensis/
Elderberries are easy to propagate. My preferred method is to wait for the plants to send out roots that come up as new stems some distance from the main shrub. I dig these up and transplant them. This does take a few years for the original seedlings to grow into mature plants before they are able to spread.
Another method is to propagate using cuttings. Here is an excellent article on how to root cuttings. https://normsfarms.com/blogs/growing-and-harvesting-elderberry/how-to-root-elderberry-cuttings
Elderberry is also an excellent plant for wildlife, especially for birds. Once the berries ripen it is a race to see who will get them. The orchard owner or the birds.
Below are photos of elderberry in our home orchard. Unfortunately, I do not have photos of ripe berries.
